1. Field of the Invention
This invention relates to photodeformable materials which when exposed to actinic radiation display deformations with dilations of about 35% in each dimension or, stated another way, a volume change of about 146% for any unit volume. More specifically, the invention is directed to a composition of matter comprising a polymeric backbone structure having a photoionizable compound attached thereto, and to a method of preparing relief images using said composition.
2. Prior Art
Mechano-chemical behavior of polymeric materials are well known. For example, the dilation and contraction of synthetic fibers due to changes in the state of ionization of polyelectrolytic gels have been observed as early as 1950. See for example the publication to W. Kuhn et al entitled "Reversible Dilation and Contraction by Changing the State of Ionization of High Polymer Acid Networks," Nature 165, 514 (1950). It is shown there that the expansion of polyacrylic acid gels were induced by suspension in alkali solutions while restoration of the original size took place when the solution was titrated with acid. Similar results were noticed by a Katchalsky et al in the publication entitled "Polyvinylphosphate Contractile Systems," Nature 166, 267 (1950), where it is shown that threads of polyvinylphosphate on the addition of strong alkali elongated to about three times their original lengths.
More recently, mechanical deformations in polymeric materials have been observed when they have been exposed to actinic radiation. More specifically, these materials have been shown to undergo a mechanical-photochemical behavioral change. For example, in the publication to P. H. Vanderwijzer et al entitled "Photochromic Polymers" J. Polymer Sci. 22, 231 (1968) and the publication to G. Smets entitled "Photochromic Behaviour of Polymeric Systems and Related Phenomena", Journal Appl. Chem. 30, 1 (1972), a photochromic spiropyran polymer displayed a 3% light induced deformation. Deformations as much as 1.2% has been shown by G. Van Der Veen et al in the publication entitled "Photoregulation of Polymer Conformation. A Model Study of Biology," Polyelectrolytes E. Selegny Edidor, D. Reidel Publishing Company, P. 483 (1974), taught that poly(methyacrylic acid) gels buffered with solutions of trans-p-(trimethylammonium) azobenzene iodide, a cis-trans photoisomerizable dye showed a 1.2% elongation when irradiated for ten minutes with a focused intense source of light. While the prior art has given examples of mechancophotochemical changes in polymeric materials, these changes have been too slight to be meaningful for any practical application. What has been discovered here is that the composition hereinafter disclosed will undergo deformations with dilations of as high as about 35% in each dimension or stated another way will undergo a volume change of about 146% for any unit volume. These materials can be used to form relief images thus may find applications in printing. Similarly, since relief images of three dimensions can be obtained there may be used for information storage as well as holographic information storage.